Introduction

The MG04 series offers a capacity increase to 5TB for Toshiba's nearline datacenter HDD offerings. The new 5TB model features five 1TB platters that deliver a 24% increase in the data transfer rate (up to 205MB/s) in comparison to the previous generation MG03SCA400.

The 7,200-RPM MG04 series is available in 6Gb/s SAS and SATA models (MGO4SCA and MG04ACA, respectively), and is designed to satisfy workload requirements for cloud applications, mid-tier servers, and high-capacity data center storage systems. Other manufacturers are already offering 6TB products, and Toshiba has a second-generation MG04 coming in Q1 2015 that will bring them up to speed with their own 6TB product. The MG04 refresh will also add a 12Gb/s connection.

The MG04SCA products provide an UBER rating of one per 10^15, and feature a 64MB FIFO ring buffer. The series also features Persistent Write Cache technology (PWC). PWC leverages the EMF energy in the spindle motor (produced by spindle rotation) to power data-loss protection circuitry. This comes in particularly handy for Advanced Format 512e models that have read-write-modify data in cache during an unexpected power loss. PWC flushes read-write-modify data down to a non-volatile cache, and restores the data when power is re-applied to the drive.

The MG04 series offers 512e and 4K Native (4Kn) models, and our sample marks the first HDD with the 4Kn format in our lab. 4Kn HDDs first debuted in April of 2014, and are already spreading into the datacenter. The 4Kn format is required to address several challenges that have cropped up as HDD density has increased. 4k sector size increases format efficiency, and thus density, by requiring less space for redundant header areas. 512-byte sectors have also become physically smaller as drive capacity increases, which causes media defects of the same size to incur damage to a larger amount of data. This increases ECC requirements. 4K sectors ease error correction requirements for media defects, and also expand error correction capability by providing more room for ECC data.

The industry has already largely moved to physical 4K sectors with Advanced Format 512e drives. These drives expose themselves to the host as logical 512-byte sectors, but an internal emulation layer translates the data to the physical 4K sectors. This emulation layer can introduce a read-write-modify process when writing data, which negatively affects performance.

The 4Kn format exposes the sectors to the host logically, and physically, at its actual 4K size. This removes the translation layer, and provides performance benefits for files 4K and larger, but 512e drives still hold an advantage for smaller file sizes. Not all applications and operating systems have 100% compatibility with 4Kn drives as of yet, but compatibility is expanding as the industry bows to the inevitability of the 4Kn format. We caution readers to assure their OS, applications, and hardware are 4Kn compatible before deploying 4Kn HDDs.

The nature of the 4Kn format will provide performance advantages over the 512e Seagate and HGST HDDs in our test pool. Format and capacity variations require consideration during performance and power consumption analyses. Let's get the MG04SCA500A on the bench for our first look at a 4Kn HDD.

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